Testing for Anions and Cations

Flame test sample preparation

• Use a damp splint or cleaned, moistened wire.

• Use a dry splint or uncleaned wire.

• Use a plastic stick or dry cotton swab.

• Use a metal rod without cleaning.

Charge of anions

• Positive

• Neutral

• Negative

• Variable

Test for Fe²⁺ ions

• Add aqueous sodium hydroxide; observe green precipitate: @@Fe^{2+} + 2OH^{-} → Fe(OH)_{2}@@

• Add hydrochloric acid; observe a colorless solution

• Add barium chloride; observe a white precipitate

• Add silver nitrate; observe a yellow precipitate

Flame test equipment needed includes...

• Bunsen burner, splint or flame test wire.

• Microscope, test tubes, and beakers.

• Thermometer, pH meter, and pipettes.

• Centrifuge, spectrophotometer, and gloves.

Colour of flame for copper

• Red

• Blue/green

• Yellow

• White

Charge of cations

• Negative

• Neutral

• Positive

• Variable

Wire used to carry out a flame test

• Copper

• Aluminum

• Nichrome

• Iron

Chemical formula for iron(III) hydroxide

• Fe(OH)_{2}

• Fe(OH)_{3}

• Fe(OH)_{4}

• Fe(OH)_{5}

Result of adding aqueous barium chloride to Sulfate (SO₄²⁻)

• White precipitate formed.

• Yellow solution formed.

• No reaction occurred.

• Gas evolved.

What is the color of the precipitate formed when adding silver nitrate to Bromide (Br⁻)?

• White precipitate formed.

• Yellow precipitate formed.

• Cream precipitate formed.

• Red precipitate formed.